De-tert-butylation of poly(N-tert-butyl-N-n-propylacrylamide): Stereochemical analysis at the triad level

The stereochemical analysis of polymers derived from N,N-disubstituted acrylamides is usually difficult. The diad tacticity can be determined from the ¹H nuclear magnetic resonance (NMR) signals of the main-chain methylene groups. However, the splitting because of the configurational sequences is poor, even in ¹³C NMR, which does not allow determination of the tacticity at the triad level. In contrast, the stereochemical analysis of polymers derived from N-monosubstituted acrylamides is easily conducted and the triad tacticity can be determined from the ¹³C signals of the main-chain methine groups. Thus, stereochemical analysis of N,N-disubstituted polymers should be able to be conducted if the polymers are transformed into N-monosubstituted polymers with retention of the configurational sequence. Poly(N-tert-butyl-N-n-propylacrylamide) was radically prepared, and de-tert-butylation was conducted by treatment with scandium triflate in a mixed solvent of CH₃CN and 1,4-dioxane at 50, 80, and 110°C. ¹H NMR analysis of the resulting polymers indicated quantitative conversion after 72 hr, regardless of the temperature. ¹³C NMR analysis of the transformed polymers confirmed that the configurational sequences were retained during the reaction. Thus, the triad stereochemical analysis of N,N-disubstituted polymers was successfully conducted by de-tert-butylation as a polymer reaction, followed by ¹³C NMR analysis of the transformed polymers.     

Esterification reactions on syndiotactic poly(2-methallyl alcohol). V. Homopolymers of 2-methallyl-(L)-dipeptidates and dipeptides cleaved from them

Syndiotactic poly(2-methallyl alcohol) (sPMA) is esterified with N^α-protected (L)-α-amino acids by the DCC/HOBT method. The resulting polymer is deprotected by HBr/glacial acetic acid. A second N^α-protected (L)-α-amino acid is condensed to the free α-NH₂ of the amino acid already bound to the sPMA by a water-soluble carbodiimide in mixed aqueous/organic solution. The formed N^α-protected dipeptide polymers were hydrazinolized to yield the N^α-protected dipeptide hydrazides. Alternatively, the dipeptidate polymers were N^α-deprotected and then hydrolyzed by aqueous KOH at pH = 11.0 to yield the deprotected dipeptides. All polymers and the dipeptides were characterized by ¹H- and ¹³C-NMR and the water-soluble N^α-deprotected polymers in addition by potentiometry. The synthetic procedures open a path to defined tactic polymers with chiral oligopeptide side chains and, after their cleavage, also to oligopeptides. During synthesis, the oligopeptide is bound to a dissolved polymer chain of relatively extended macroconformation which facilitates both the accessibility and reactivity of the reaction centers as well as the precipitation and filtration after each synthesis step. © 1995 John Wiley & Sons, Inc.     

Elastic behavior of ring polymer chains

In this article, the conformational properties and elastic behaviors of ring polymers in the process of tensile elongation are investigated with the Monte Carlo method and the bond fluctuation model. The ratio of the mean‐square diameter <d²> to the mean‐square radius of gyration <S²> increases with the elongation ratio, λ, and the instantaneous shape of ring polymers is more symmetric than that of linear chains in the process of tensile elongation. Here <d²> for ring polymers rather than the mean‐square end‐to‐end distance <R²> for linear polymers is defined as the average of squared distances between two segments separated by N/2 bonds, where N represents the total number of bonds. Local quantities, that is, the mean‐square bond length <b²> and the mean bond angle <θ> increase with λ, especially for short ring chains. The <d²> and <S²> have the same relationship with the chain length, N, that is, <d²> ～ N^1.130±0.020 and <S²> ～ N^1.160±0.013 for a different λ. Some thermodynamics properties are also addressed here. The average energy per bond <U> decreases with λ and the average Helmholtz free energy and elastic force f increase with λ, especially for short ring chains. Comparisons with linear chains are also made. These investigations may provide insight into the elastic behaviors of ring polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 223–232, 2005     

Functional monomers and polymers. CXXI. Methylation and interaction studies on adenine containing polymethacrylate derivatives

Studies of the methylation of polymethacrylate derivatives with adenine bases were made in comparison to those with uracil bases. The polymethacrylate derivatives with adenine bases were methylated by using methyl iodide in dimethyl sulfoxide solution to produce polymers that contained N¹-methyladenine and N¹, N⁶-dimethyladenine units. The products were identified by spectroscopic data and by preparing their model compounds. The methylated polymers obtained were further applied in a study of polymer complex formation with uracil-base polymers.     

Hole‐transporting host‐polymer series consisting of triphenylamine basic structures for phosphorescent polymer light‐emitting diodes

A series of novel styrene derived monomers with triphenylamine‐based units, and their polymers have been synthesized and compared with the well‐known structure of polymer of N,N′‐bis(3‐methylphenyl)‐N,N′‐diphenylbenzidine with respect to their hole‐transporting behavior in phosphorescent polymer light‐emitting diodes (PLEDs). A vinyltriphenylamine structure was selected as a basic unit, functionalized at the para positions with the following side groups: diphenylamine, 3‐methylphenyl‐aniline, 1‐ and 2‐naphthylamine, carbazole, and phenothiazine. The polymers are used in PLEDs as host polymers for blend systems with the following device configuration: glass/indium–tin–oxide/PEDOT:PSS/polymer‐blend/CsF/Ca/Ag. In addition to the hole‐transporting host polymer, the polymer blend includes a phosphorescent dopant [Ir(Me‐ppy)₃] and an electron‐transporting molecule (2‐(4‐biphenyl)‐5‐(4‐tert‐butylphenyl)‐1,3,4‐oxadiazole). We demonstrate that two polymers are excellent hole‐transporting matrix materials for these blend systems because of their good overall electroluminescent performances and their comparatively high glass transition temperatures. For the carbazole‐substituted polymer (T_g = 246 °C), a luminous efficiency of 35 cd A^?1 and a brightness of 6700 cd m^?2 at 10 V is accessible. The phenothiazine‐functionalized polymer (T_g = 220 °C) shows nearly the same outstanding PLED behavior. Hence, both these polymers outperform the well‐known polymer of N,N′‐bis(3‐methylphenyl)‐N,N′‐diphenylbenzidine, showing only a luminous efficiency of 7.9 cd A^?1 and a brightness of 2500 cd m^?2 (10 V). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3417–3430, 2010     

Polymerization of N-(fluoro phenyl) maleimides

Poly(N-aryl maleimide)s of characteristic structures have been synthesized and some of their physical properties studied. These include N-(2-fluoro phenyl), N-(3-fluoro phenyl), N-(4-fluoro phenyl), N-(2,4-difluoro phenyl), N-(2,5-difluoro phenyl), N-(2,3,5,6-tetrafluoro phenyl), and N-(pentafluoro phenyl). The polymerization of N-(fluoro phenyl) maleimides by free-radical initiation in bulk or in solution and by anionic catalyst have been studied to compare the characteristics of polymerization by γ-ray irradiation with that by free-radical initiation. The polymers were characterized by elemental analysis, intrinsic viscosity, spectroscopy (IR and NMR), programmed thermogravimetric analysis, and x-ray diffraction. Spectra of polymers prepared by radiation and anionic polymerization were nearly identical with those of polymers prepared by free-radical polymerization initiated by AIBN in bulk or in solution and by the self-initiated thermal polymerization. A variety of reaction conditions were tried, but all attempts to change the molecular structure of the polymers were unsuccessful. Rates of thermal degradation for poly[N-(fluoro phenyl) maleimide]s have been analyzed by using a multiple-heating-rate procedure. Overall activation energy, order of reaction, and frequency factor have been evaluated. On the basis of the comparison between the overall activation energy of the thermal degradation of poly[N-(fluoro phenyl) maleimide]s and NMR spectra of their corresponding monomers, it can be concluded that the ¹H shifts due to ethylenic protons are so characteristic in sign and magnitude as to be useful in thermal stability elucidation. Some qualitative explanations were given on the stability of these polymers as affected by the type and size of the substituent. The x-ray diffractograms of all samples show two rather broad peaks indicative of noncrystalline structures. The location of the peaks does not depend upon preparation conditions and temperature. Poly(N-maleimide)s of fluoroanilines have not been hitherto described.     

Thermotropic liquid crystalline polymers. II. Polymers with amino acid fragments in the side chains

The comblike polymers, poly(N^ε-methacryloyl-N^α-acyl) derivatives of L -lysine, which contain amino acid fragments and long sequences of methylene groups in the side chain, were synthesized. This article, which is based on x-ray data, differential thermal analysis, and optical microscopy, describes the structure of these polymers and their properties. It also shows that the combination of anisodiametric side groups with a “rigid” matrix of main chains leads to a liquid crystalline structure of examined polymers.     

Pseudo-poly(amino acid)s: study on construction and characterization of novel chiral and thermally stable nanostructured poly(ester-imide)s containing different trimellitylimido-amino acid-based diacids and pyromellitoyl-tyrosine-based diol

A new class of chiral and potentially biodegradable poly(ester-imide)s (PEI)s as pseudo-poly(amino acid)s (PAA)s bearing natural amino acids in the main chain was synthesized. In this investigation, N,N′-(pyromellitoyl)-bis-(L-tyrosine dimethyl ester) as a biodegradable optically active diphenol and synthesized trimellitic anhydride-derived dicarboxylic acids containing different natural amino acids such as S-valine, L-methionine, L-leucine, L-isoleucine, and L-phenylalanine were used for direct polyesterification. With the aim of tosyl chloride/pyridine/N,N′-dimethylformamide system as a condensing agent, the new optically active PEIs were obtained in good yields and moderate inherent viscosity up to 0.42 dL/g. The obtained polymers were characterized with FT-IR, ¹H-NMR, X-ray diffraction (XRD), field emission scanning electron microscopy, elemental, and thermogravimetric analysis techniques. These polymers show high solubility in organic solvents, such as N,N′-dimethyl acetamide, N-methyl-2-pyrrolidone, and sulfuric acid at room temperature, and are insoluble in solvents, such as methylene chloride, cyclohexane, and water. Morphology probes showed these pseudo-poly(amino acid)s were noncrystalline and nanostructured polymers. On the basis of thermogravimetric analysis data, such PAAs are thermally stable and can be classified as self-extinguishing polymers. In addition due to the existence of amino acids in the polymer backbones these pseudo-PAAs not only are optically active but also are expected to be biodegradable and therefore could be classified under eco-friendly polymers.     

Synthesis,structure, cytotoxic activities,and DNA-binding of 1-D copper(II) and zinc(II) coordination polymers

Two 1-D coordination polymers have been synthesized and identified as [Zn(ox)(en)] _n (H₂O)_{2 n} (1) and [Cu₂(dmeo)(N₃)₂] _n (2), where en represents diaminoethane, ox and dmeo stand for dianions of oxalic acid and N,N′-bis[2-(dimethylamino)ethyl]oxamide, respectively. Polymer 1 was characterized by elemental analysis, molar conductance measurement, IR and electronic spectra, and single-crystal X-ray diffraction. Polymer 1 consists of 1-D chains bridged by oxalate. The Zn^II can be described as a distorted octahedral environment and the Zn^II···Zn^II separation through the μ-oxalato-bridge is 5.5420(9)?Å. Hydrogen bonds assemble the coordination polymers to a 3-D supermolecular structure. The crystal structure of 2 has been reported previously. However, the bioactivities were not studied. The DNA-binding properties and cytotoxic activities of the two coordination polymers are investigated. The results suggest that the two polymers interact with HS-DNA in groove binding with binding affinity following the order of 1?>?2, which is consistent with their anticancer activities.     

Bis­[N,N′‐bis­(di­phenyl­methyl­ene)ethyl­enedi­amine‐κ2N,N′]copper(I) di­chloro­cuprate(I)

The 1:1 adduct of N,N′‐bis­(di­phenyl­methyl­ene)­ethyl­enedi­amine (bz₂en) with copper(I) chloride, viz. [Cu(C₂₈H₂₄N₂)₂][CuCl₂], has been synthesized. The structure contains cationic moieties of Cu^I ions (Cu on a twofold axis) coordinated to four N atoms of two bz₂en mol­ecules (in a distorted tetrahedron) and linear di­chloro­cuprate(I) anions (with Cu on an inversion centre). These cations and anions are packed in columns along b. The packing of the cation and anion columns involves a significant C—H⋯Cl interaction and four short intermolecular C—H⋯π contacts, two of which are between cation columns.     

Morphology and interactions of polymer brush‐coated spheres in a polymer matrix

Using a real space implementation of the self‐consistent field theory, we calculated the morphology and interactions of spherical nanoparticles with radius R_p that are grafted by polymer chains of N monomers immersed in a chemically identical polymer melt of polymerization index P. The calculation shows that, for big particles (R_p ? N^1/2a, with a the segment size), the interactions and density profiles of the grafted layers are that of brushes at flat interface; While for small particles (R_p ? N^1/2a), the interactions and density profiles are characteristic of star polymers. In the case of intermediate grafted chain lengths, that is, R_p ～ N^1/2a, we found that the grafting density of the polymers and the radius of the spherical nanoparticles are both important in determining the structure and interactions of the grafted layers. Our findings suggest possible ways to tailor the structure and interactions of the nanoparticles to benefit the fabrication of polymeric nanocomposites. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2811–2820, 2006     

Isotactic rac‐Lactide Polymerization with Copper Complexes: The Influence of Complex Nuclearity

Diiminopyrrolide copper alkoxide complexes, LCuOR (OR¹=N,N‐dimethylamino ethoxide, OR²=2‐pyridyl methoxide), are active for the polymerization of rac‐lactide at ambient temperature in benzene to yield polymers with M_w/M_n=1.0–1.2. X‐ray diffraction studies showed bridged dinuclear complexes in the solid state for both complexes. While LCuOR¹ provided only atactic polylactide, LCuOR² produced partially isotactic polylactide (P_m=0.7). The difference in stereocontrol is attributed to a dinuclear active species for LCuOR² in contrast to a mononuclear species for LCuOR¹.     

Mutual Transformations of Isomers in N-Methyl-5-vinyltetrazole Copolymers

Mutual transformations of N ¹ and N ² isomeric derivatives of 5-vinyltetrazole polymers in the absence of a solvent were studied.     

Power‐law scaling of structured poly(p‐xylylene) films deposited by oblique angle

This study describes the evolution and growth of structured polymers by oblique angle deposition of poly(p‐xylylene) (PPX) derivatives. The deposition of structured PPX polymers have been demonstrated recently, but the mechanism of growth has not been studied. Here, we provide experimental evidence for the growth of structured PPX polymers by an atomic force microscope, electron microscope, and a profilometer. Individual columns expand with respect to their heights according to a power‐law, d = ch^p, where d is the column diameter, c and p are constants, and h is the height of a column. Values of p for structured poly(chloro‐p‐xylylene), poly(trifloroacetly‐p‐xylylene‐co‐p‐xylylene), and poly(bromo‐p‐xylylene) films are estimated as 0.11 ± 0.01, 0.15 ± 0.01, and 0.18 ± 0.01, respectively. This result is different from the traditional oblique angle deposition processes of nonpolymeric materials where the surface diffusion is low. Further analysis with two‐dimensional power spectral density (PSD) method showed that the ordering of columns is quasi‐periodic. Additionally, the X‐ray and transmission electron microscope characterization of the columns revealed that the columns are semicrystalline. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 640–648, 2008     

Monomer reactivity ratios for acrylonitrile–methyl acrylate free‐radical copolymerization

Nonlinear monomer reactivity ratios for the homogeneous free‐radical copolymerization of acrylonitrile and methyl acrylate were determined from ¹H NMR and real‐time Fourier transform infrared (FTIR) analyses. All ¹H NMR data were obtained on polymers isolated at low conversions (<10%), whereas the FTIR data were collected in situ. The copolymerizations were conducted in N,N‐dimethylformamide at 62 °C and were initiated with azobisisobutyronitrile. The real‐time FTIR technique allowed for many data points to be collected for each feed composition, which enabled the calculation of copolymer compositions (dM₁/dM₂) with better accuracy. Monomer reactivity ratios were estimated with the Mayo–Lewis method and then were refined via a nonlinear least‐squares analysis first suggested by Mortimer and Tidwell. Thus, monomer reactivity ratios at the 95% confidence level were determined to be 1.29 ± 0.2 and 0.96 ± 0.2 for acrylonitrile and methyl acrylate, respectively, which were valid under the specific system conditions (i.e., solvent and temperature) studied. The results are useful for the development of acrylonitrile (<90%) and methyl acrylate, melt‐processable copolymer fibers and films, including precursors for carbon fibers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2994–3001, 2004     

Cellulose wet wiper sheets prepared with cationic polymer and carboxymethyl cellulose using a papermaking technique

Carboxymethyl cellulose (CMC)-rich cellulose sheets were prepared with a cationic retention aid, poly[N,N,N-trimethyl-N-(2-methacryloxyethyl)ammonium chloride] (PTMMAC), using a papermaking technique. When 5% PTMMAC and 5% CMC were added to cellulose slurries, approximately 94% of the polymers were retained in the sheets by formation of polyion complexes between the two polymers. When the PTMMAC/CMC/cellulose sheets were soaked in solutions consisting of ethanol, water and calcium chloride (EtOH/H₂O/CaCl₂) with a weight ratio of 75:24:1, almost all PTMMAC and CMC molecules remained in the sheets, forming the structures of PTMMAC-N⁺Cl⁻ and CMC-COO⁻Ca²⁺Cl⁻ without dissolution of these molecules in the soaking solution. Thus, PTMMAC, CMC and calcium contents in the sheets were able to be determined on the basis of these PTMMAC and CMC structures from analytical data such as nitrogen, calcium and chlorine contents. The trade-off properties between sufficient wet strength in use and water-disintegrability after use can be added to the PTMMAC/CMC/cellulose sheets by selecting weight ratios of the EtOH/H₂O/CaCl₂ solution used as the impregnation liquid.     

Photoconductivity and hole transport in polymers of aromatic amine-containing methacrylates

Substantial hole transport can be achieved in organic polymers simply by incorporating aromatic amine groups into the monomer. Hole mobilities similar to or greater than those in poly(N-vinyl-carbazole) (PVK) were measured in a series of high molecular weight arylamine-substituted polymethacrylates. The hole transport in these polymers is electric-field-dependent as in PVK, varying between E and E² within a range of 4 × 10⁴ ? ～9 × 10⁵ V/cm. The polymers also exhibit carrier generation in ultraviolet (UV) light in the range of absorption. Synthesis of the monomers, their polymerization, and the general properties of these polymers are discussed.     

Effect of alkyl substituents structures and added ions on the phase transition of polymers and gels prepared from methyl 2‐alkylamidoacrylates

The effects of structure alteration of alkyl groups and addition of ions to solutions of new thermosensitive polymer series of poly(methyl 2‐alkylamidoacrylate)s were investigated. Potential advantages of the thermosensitive polymers are their simplicity of functionalization and transition temperature control that result from their unique α,α‐disubstituited structures. Poly(methyl 2‐propionamidoacrylate) (PMPA) and poly(methyl 2‐isobutyracrylate) (PMIBA) were thermosensitive polymers, and poly(methyl 2‐acetamidoacrylate) and poly(methyl 2‐n‐butyramidoacrylate) were completely water‐soluble and ‐insoluble, respectively. The PMIBA solution showed endotherm during the phase transition, while endotherm was not detected for PMPA. The difference between the two polymers resulted from the size of the hydrophobic groups. MPA gel was prepared by copolymerization with N,N′‐methylenebis(acrylamide) and temperature‐induced volume change of the gel was continuous. The salting‐out effect of inorganic ions on PMPA solution and MPA gel followed the Hofmeister series. The inorganic (I^? and SCN^?) and organic ions (ⁿPr₄N⁺ and ⁿBu₄N⁺), which showed the salting‐in effect, were indicated to directly interact with PMPA chains. These ions widened the temperature range of the phase transition of the PMPA solutions. This reduced cooperativity of the phase transition was caused by size decrease of cooperative domains, which resulted from the interaction of the ions with the polymer. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4942–4952, 2005     

Cationic polyelectrolytes. I. Soluble polymers prepared from reaction of chloromethylated polystyrene with tris(2-hydroxythyl)amine

The reaction of chloromethylated polystyrene with tris(2-hydroxyethyl)amine in N,N-dimethylformamide is described for the conditions to prepare soluble reaction products. The groups of the quaternary ammonium salt, which appear in the first stage of the reaction, transpose to the amino-ether groups. The reaction was followed by elementary analysis, IR and ¹H-NMR spectra, and viscosimetric measurements for nondialyzed and dialyzed samples. The presence of the tertiary amine groups on obtained polymers was also shown by titration. The polymers from the reaction of chloromethylated polystyrene with tris(2-hydroxyethyl)amine reacted easily with benzyl chloride.     

Studies on synthesis and in vitro biodegradability of novel optically active nanostructure poly(ester-imide)s containing <Emphasis Type="SmallCaps">l</Emphasis>-phenylalanine and <Emphasis Type="SmallCaps">l</Emphasis>-isoleucine linkages

A series of biodegradable functional amino-acid-based poly(ester-imide)s (PEI)s were designed and synthesized by the direct polycondensation reaction of chiral diacids composed of naturally occurring α-amino acids with 4,4′-thiobis(2-tert-butyl-5-methylphenol) in the presence of tosyl chloride, pyridine, and N,N-dimethylformamide as a condensing agent. These new chiral polymers were characterized with respect to chemical structure and purity using specific rotation experiments, FT-IR, ¹H-NMR, techniques, and elemental analysis. The surface morphology of these polymers was investigated by field emission scanning electron microscopy. The result indicated nanoscale morphology of the obtained polymers. Thermal stability and the weight loss behavior of the resulting PEIs were studied by TGA techniques. All PEIs showed no significant weight loss below 400 °C in a N₂ environment. The monomers and prepared polymers were co-cultivated with airborne fungal spores in culture media to study their biological activity. Soil burial test was also used for evaluation of their biodegradation behavior. The results showed that the synthesized monomers and their derived polymers are biologically active and that their degradation products are probably nontoxic to microbial growth.